Loom protection apparatus



July 31, 1956 R. a. APPLEGATE :nu. 2,

- LOOM PROTECTION APPARATUS Filed Dec. 9, 1954 I'-nlannlinnlnznu- 4 I .l4

h Time in C cle t M WITNESSES INVENTORS Rcbert B. Applegote and WilliamR.Durrett. 7 WZTW ATTORNEY nited States Patent LooM PROTECTION APPARATUSRobert B. Applegate, Cleveland, and William R. Durrett,

Berea, Ohio, assignors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Penn sylvania Application December 9,1954, Serial No. 474,128

9 Claims. (Cl. 139341) Our invention relates to improvement in motorcontrol systems and more particularly to improvements in loom protectiondevices wherein operation of a loom is stopped if the shuttle (or yarncarrier) thereof is not correctly positioned at a given instant in theoperating cycle of the loom.

In order to prevent the shuttle, or yarn carrier, of a loom frombreaking threads in the warp shed thereof, it is essential that theshuttle complete its flight between the shuttle boxes before the warpthreads are moved into the path of the yarn carrier. Should the shuttlebe stopped in the warp shed or be appreciably delayed in its operatingcycle for any reason, warp threads will almost inevitably be broken andthe shuttle and other loom components may be damaged unless the loom isinstantly stopped. Manifestly, it is desirable that such delay bedetected before the shuttle reaches the shuttle box towards which it istraveling if sufiicient time is to be provided for the loom to bestopped before damage occurs.

Typical of systems for loom protection that have been used in the pastis that described in U. S. Patent 2,664,116 to A. C. Krukonis. Thereinthere is described an arrangement wherein a photoelectric cell isutilized to detect the passage of the loom shuttle at a pointapproximately midway between shuttle boxes. A light source is pulsedduring the portion of the operating cycle of the loom at which theshuttle should be passing between the light source and the photoelectriccell. If the shuttle is delayed in its flight, the resulting increase inphotoelectric cell current produced by light rays from the light sourceimpinging thereon will be efiective to energize braking apparatusassociated with the drive motor of the loom. A prime disadvantage ofthis system is that the necessity of mounting the photoelectric tube andthe light source on the loom renders these components susceptible todamage due to shock, vibration, etc. Inasmuch as failure of either thelight source or the photoelectric tube would mean that the loom wouldnot be stopped should faulty operation occur, it can be seen thattotally reliable protection would not be provided for the loom.Additionally, dirt, lint and like particles prevalent in locales whereinlooms are generally utilized tend to collect on the photocell and impairoperation thereof by at least partially blocking the light rays passingfrom source, to cell. As a result, the photoelectric cell must beperiodically cleaned by the loom attendant. An additional that isrugged, reliable, and employs a minimum number of mechanical movingparts.

Another object of our invention is to provide a loom protection systemthat will effectively prevent damage to a loom and to the material beingfabricated thereby when the yarn carrier is delayed or undulyaccelerated in its flight between shuttle boxes.

A further object is to provide loom protection apparatus that will stopoperation of the loom in the event of failure of any of the componentparts of the detection apparatus.

A still further object is to provide loom protection apparatus forstopping operation of a loom when the shuttle is delayed or undulyaccelerated in its flight between shuttle boxes wherein the apparatusdetecting the faulty movement of the shuttle will not be affected bydirt, lint and like particles that may collect thereon.

Yet another object is to provide loom protection apparatus forprotecting a loom and the material fabricated thereby against damagecaused by delayed or unduly accelerated action of the loom shuttlewherein the equipment for detecting such faulty operation has inherentlong life and requires a minimum of maintenance and periodic inspection.

Other objects and features of our invention will become apparent uponconsideration of the following description when taken in connection withthe accompanying drawing wherein: I Figure l is a front elevation of aloom, parts being broken away, having the invention applied thereto;

Fig. 2 is an enlarged vertical section on line II-II of Fig. 1, showingthe lay in full lines in the position which it occupies whiletheshuttleis in flight through the warp shed and in broken lines when thelay is in front center;

Fig. 3 is an enlarged View of a. portion of the lay as shown in Fig. 1;

. Fig. 4 is a schematic diagram of a form of electric circuit forcarrying our invention into effect; and

Fig. 5 is a line diagram showing the portions of a cycle of operation ofthe loom over which indicated switches in the schematic diagram of Fig.4 are closed.

In one aspect of our invention, a radioactive material is implanted inthe shuttle or yarn carrier, and a radioactivity detector such as aGieger-Mueller tube is stationed adjacent the point in the path of the.carrier whereat the carried should be passing at a given instant in theshortcoming of the system referenced above is that the I life of thelight source will be considerably shortened as a result of pulsingthereof, which will require a rigid preventive maintenance program. inview of the incomplete loom protection noted above. Still further, somewarp sheds are sodense that very little light can penetrate cycle ofoperation thereof. If the carrier is on time during a given cycle ofoperation, output pulses from the radioactivity detector actuate controlapparatus that permits the loom to continue to operate through anothercycle of operation. If, however, the carrier is either late or early inits cycle of operation, no pulses will appear at the output of thedetector over the time interval assigned for the passage of the carrierby the point at which the detector is stationed, and the controlapparatus will be actuated to break the motor by plugging thereof orother convenient means.

With reference now to Fig. 1, there is shown a loom having left andright loom sides 1 and 35, respectively, which support a rocker shaft 12for left and right side lay-swords 9 and 22, respectively,-which supportthe lay designated by the reference numeral 29.

The lay is swung backwardsand forwards in the loom by power imparted toit from a. top shaft 27 through connectors, one of which'is designated.51 in Fig. 2.

' The top shaft is driven. by means of motor 47 through a gear trainincluding gears 45, 41 and 37. The bottom shaft 1.5 is driven fromtopshaft 27 through a gear train. including gears 36-and 43. Pickingarms 13 and- 46 are secured toshaft 15 forcooperation with picking 3cams 11 and 42, respectively, operatively connected to picker sticks 5and 38, respectively. The picker sticks operate one at a time andusually during the backward stroke of the lay when it is at or near itstop center position approximate midway between its extreme front andback positions. The shuttle aligned with a picker stick will bepropelled by it from one end of the loom to the other end, causing it topass through a warp shed designated as S (Fig. 2) comprising upper orlower planes or groups of warp threads 20 and 22. The threads passthrough reed 23, the lower end of which is positioned by the lay beammember 18 and the upper end of which is positioned by a hand rail member60. As shown in Fig. 2, hand rail member 60 is supported by arm 62 whichextends upward from the lay structure 29.

Implanted in the bottom of shuttle 33 is a slug or a pellet 49 of aradioactive material, preferably a betaray source such as Thallium 204.Approximately midway along the path of travel of the shuttle near thetop edge of the lay beam 29 there is provided a cavity 31 which opensonto the top edge of the lay beam through channel 32. Within the cavity31 there is provided a radiation detector 50, such as an ionizationchamber, a Gieger-Mueller tube, or a proportional counter, whichdetector comprises an anode 53, a cathode 52 and an envelope orprotective enclosure. To prevent the detector from being actuated whilethe shuttle is at a distance from the detector, except in the vicinityof channel 32, the cavity may be lined with a sheath of lead or othermaterial through which radioactive emanations can penetrate only withextreme difiiculty. This lining may or may not be necessary depending onthe type of radioactive material embedded in the shuttle. Ionizingparticles from the radioactive material should be able to penetrate tothe radiation detector only when the shuttle is passing directly overchannel 32.

The operation of motor 47 is controlled by the circuitry shown in Fig.4. Power for the motor is provided from 3-phase alternating currentlines 168, 170 and 172 which are respectively connected to terminals174, 176 and 178 of motor 47 by normally open contactors 158, 156 and154 of relay 148. Braking or plugging current for the motor is providedfrom D. C. lines 164 and 166 which are connected to motor terminals 174and 178 through normally closed contactors 162 and 160.

The actuating coil 150 of relay 148 is energized by the circuitrydescribed below. The output pulses from radiation detector 50 areamplified by means of pulse amplification circuit 71. The anode 53 isconnected to the control grid 74 of pulse amplifier tube 70 and thecathode 52 is connected to the negative terminal of a high voltage powersupply (not shown) which supplies proper voltage for operating theradiation detector. Grid-leak resistor 78 is connected between controlgrid 74 and cathode 72 of amplifier tube 70 which may be of the 6SH7type. A voltage divider circuit, including serially-connected resistors86, 82 and S0 in the order named, is connected between the positive andnegative terminals of the high voltage power supply. Screen grid 76 ofamplifier tube 70 is connected to the juncture of resistances 82 and 86and cathode 72 is connected to the juncture of resistances 80 and 82.Screen bypass condenser 84 is connected between screen grid 76 andcathode 72. Plate potential for amplifier tube 70 is provided from thepositive terminal of the high voltage power supply through loadresistance 88.

The output pulses from amplifier 71 are converted to square Wave form bysaturating amplifier 91. This amplifier includes vacuum tube 92 whichmay be a 6SH7 type tube having a cathode 96, control grid 94, screengrid 98, plate 93 and a suppressor grid 95 which is connected directlyto the cathode. Grid leak resistor 105 is connected between control grid94 and ground and pulses appearing across load resistor 88 of amplifier71 are coupled to control grid 94 by means of coupling capacitor 90. Alow voltage power supply (not shown) is connected to plate 93 throughdropping resistor 102 and to screen grid 93 through dropping resistor1M. Cathode resistor 106 is connected between cathode 96 and tap oflow-voltage voltage-dividing resistance 136. in effect, amplifier 91 canbe seen to be a cathode follower.

The square wave output pulses appearing across resistance 106 arecoupled to a clipping and summing circuit 1 9 by means of couplingcapacitor 104. The out put pulses are clipped by means of rectifier 112which is connected between coupling capacitor 194 and ground. Theclipped output pulses are coupled by means of halfwave rectifier 114 toa summing capacitor 116 which is shunted by resistor 118. The otherterminal of capacitor 116 is connected directly to ground. The value ofcapacitors 116 and 104 and resistor 118 are chosen so as to permit anaccumulation of D. C. voltage across capacitor 116 only when a rapidsuccession of pulses appear at the output of radiation detector 50 suchas will occur when the radioactive slug in the shuttle is directly abovethe detector. This minimizes the amount of shielding required around theradiation detector.

The output voltage across resistance 118 is coupled to the grid 132 ofthyratron 128 through resistor 122 and switch 17. The cathode 134 of thethyratron is connected to tap 138 of voltage divider 136, thus allowingadjustment of the thyratron plate voltage. Voltage dividing resistor 136is connected to the positive terminal of the low voltage source by meansof resistor 108 and to ground, the negative terminal of low voltagesupply likewise being connected to ground. The actuating coil of relay148 is connected between plate 130 of thyratron 128 and the juncture ofresistances 103 and 136 through voltage dropping resistor 12% Plate 139is connected to ground through switch 19 and through serially-connectedresistor 146 and switch 21. Condenser 141 is connected between plate 130and ground to minimize the efifect of plate voltage surges.

Switches 17, 1'9 and 21 are actuated by cams on top shaft 27. Theswitches are closed for various predetermined portions of each operatingcycle of the loom as shown generally by the shaded areas in Fig. 5.Switch 21 is closed from the beginning of a cycle to a time t2corresponding approximately to the instant at which the trailing edge ofthe shuttle 33 passes over radiation detector 50 when running normally.At time t1, corresponding approximately to the instant at which theleading edge of shuttle 33 passes over detector 50 when runningnormally, switch 17 is closed and remains closed until time 22. At atime t3, subsequent to time t2, switch 19 is closed to extinguish thethyratron. The time interval between t2and I3 is suflicient to allow themotor 47 to brake to a stop in the event that the shuttle is early orlate in its flight between shuttle boxes. At some time t4, subsequent totime t3, switch 21 is closed and remains closed fior the remainder ofthe cycle. Switch 19 opens very soon after switch 21 closes, prior tothe end of the cycle. Switch 19 also may close momentarily afiter theclosure of switch 21 at time t4 if care is taken to prevent a voltagesurge that would trigger the thyratron. In either case, switch 19 mustopen after the closure of switch 21.

At the time of shuttle picking, the lay will be moving rearwardly and,while the shuttle is in flight through the warp shed, will reach itsback center position under correct operating conditions. The lay willthen start to move forward as the shuttle continues through the warpshed. Should the shuttle be traveling slower than usual, or should it bestopped in the Warp shed for any reason, the reed 23 will push theshuttle forwardly through the warp shed and break some of the warpthreads of the top and bottom thread groups 20 and 22 unless the loom isimmediately stopped.

Let it be assumed, however, that the shuttle is on time and that it ispassing over radiation detector 50 at the instant in the operating cyclet1 at which time switch [17 is closed and before switch 21 opens. Atrain of pulses produced by' radioactive emanations from source 49 willappear at the output of radiation detector 50 and will produce a rapidlyrising voltage on the grid of thyratron 128 (switch 17 being closed).This voltage 'will almost instantly reach a level sufiicient to fire thethyratron. While the opening of switch 21 would noranally interrupt theflow of current through relay coil 150, the firing of the thyratron andthe resulting current flow through coil 150 produced thereby issufficient to hold the relay closed, and the motor will continue inoperation. At time t2, switch 17 will open but the thyratron will remainfired; at time t3 switch 19 will close, extinguishing the thyratron, andsubsequently thereto at time t4 switch 21 will close, reestablishingthyratron plate voltage as soon as switch 19 opens. Thus, from time t3of one cycle until time t2 of the next cycle, relay 148 will remainclosed.

Assume now that the shuttle is late in its cycle so that no pulsesappear at the output of radiation detector 50 during the time intervalfrom ii to. 2. The thyratron cannot fire and inasmuch as switch 21 willbe opened at time t2, the relay 148 will drop. out. Plugging currentfrom D. C. lines 164 and 166 will almost instantly stop the motor beforeswitch 19 can close, thus protecting the loom and the. material beingfabricated thereby from damage.

It is readily apparent that the radiation detector need not be placedexactly midway between the shuttle boxes as indicated in Fig. l, but maybe placed at any position along the path traversed by the shuttle suchas may be most advantageous to prevent damage. Likewise, more than oneprotective system may be incorporated so as to monitor the flight of theshuttle at various positions. between the shuttle boxes. Additionally, acertain amount of latitude is permissible in setting the time intervalsover which switches 17, 21 and 19 are closed.

With regard to the choice of a source of radioactive material, it hasbeen determined that a beta-ray source, such as Thallium 204, is themost suitable in this particular application. Of the three types ofradiation, alpha rays are the least penetrating and have the smallestrange in air. Beta rays are more penetrating, and gamma rays are themost penetrating of the three. In order to insure safety of operatingpersonnel against contamination, it is necessary to encapsulate thesource. If an alpha ray source were used, the capsule would have to bevery thin to allow radiation to pass through, and would, therefore, bequite fragile and ill-adapted to withstand the shock and vibrationassociated with loom operation. A thick, dense warp shed could blockalpha rays as effectively as light rays. Additionally, alpha radiationis by far the most dangerous. of the three types noted above insofar asinternal or ingested exposure is concerned, and this fact combined withthe requisite thin capsule makes an alpha source highly undesirable. Asource of gamma radiation, likewise, is not particularly desirable fortwo reasons. First, it is the least efiicient ionizing agent of thethree radiation types and would tend to render the detector insensitive.to the passage of the shuttle. More important, however, is the fact thatgamma radiation is so penetrating as to require excessive shielding inorder to protect operating personnel. The range in air of gamma rays issuch that it could easily reach over to adjacent machinery. If everyloom in a work area had a radioactive source emitting gamma rays, therewould result a marked rise in the normal radiation level of the areathat could present a serious operating hazard, un-

less the radioactive source were adequately shielded.

A source of beta radiation, on the other hand, has enough penetratingability to allow strong encapsulation, and its range in air issufliciently short so that adjacent looms would be virtually unaffectedby the radiation from any one set of shuttles. A one-quarter inchthickness of wood effectively attentuates beta radiation, thus virtuallyeliminating the necessity for the shielding 54 noted above. In mostinstances, the requirement for shielding is entirely eliminated. Betaradiation emanating from channel 32 passes through the most dense warpshed virtually unaffected. The human skin stops all but the hardest ofbeta rays, thus minimizing possibilities of surface burns, evenpresuming careless handling of the radioactive source.

It is readilyapparent that our invention has achieved the objects setforth above. Failure of the radiation detector or any of the tubes. inthe. control apparatus will prevent the thyratron from firing at itsappointed time in the operating cycle of the loom so that the loom willbe instantly stopped. The detecting apparatus is inherently notafi'ected by dirt or lint inasmuch as the detector is actuated byradioactive emanations rather than. by light rays which may be masked bydirt, lint and the like. Both the radiation detector and the radioactiveemitter are inherently rugged and have long operating lifetimes. so asto require a minimum of maintenance and periodic inspection. The controlapparatus actuated by the radiation detector may be stationed at a.sufiicient distance from the loom so as to be unaifected by the. shocksand vibrations produced thereby, and should present no extraordinarymaintenance problem as. a result thereof.

Manifestly, our invention may take forms other than that specificallydescribed above. For example, the detecting head may be used as a limitswitch to control operation of a motor driven reciprocating planer, byimplantingtheradioactive source in the reciprocating planer tableandstationing the radiation detector at a position whereat the source willpass when the table is to be reversed. impulses from the detecton'aftersuitable ampli-fication, may be. used totrigger the electrical controlapparatus. norm-ally associated with the machine tool so as. to initiatethe sequence of operation of said control apparatus that reverses thedirection of operation of the planer table. Therefore, the invention isnot to be restricted to the specific. structural details, arrangement ofparts or circuit connections herein set forth, as various modificationsthereof may be effected without departing from the spirit and scope ofthis invention.

We claimas, our invention:

1. In protection means for a loom operating with a. yarn carrier whichwhen running on time passes a given point along the path thereof at agiven time in the loom cycle, radioactive means implanted in said yarncarrier, radiation detecting means stationed at a position where-atradiation particles from said radioactive means willbe detected whensaid shuttle passes said given point, pulse amplifying means responsiveto the output indications from said radiation detecting means,saturating, amplifier means adapted to produce rectangular-wave pulsesresponsive to the output of said pulse amplifying means, clipping andsumming means responsive to the output indications from said saturatingamplifier means adaptedto provide a direct voltage, the amplitude ofwhich is functionally related to the frequency of the pulses from saidradiation detecting means, thyratron means adapted to actuate means forcontinuing loom operation for an additional cycle of operation, switchmeans, actuated by said loom adapted to couple said output of saidclipping and summing means to said thyratron during a predeterminedportion of each cycle of loom operation and to extinguish said thyratronat the end of said each cycle should said thyratron be in a conductingstate thereat.

2. in protection means for a loom operating with a yarn carrier whichwhen running on time passes a given point along the path thereof at agiven time in the. loom cycle, radioactive means implanted. in said yarncarrier, radiation detecting means. stationed atv a position whereatradiation particles, fromv said radioactive means; will; be

detected when said shuttle passes said given point, pulse amplifyingmeans responsive to the output indications from said radiation detectingmeans, saturating amplifier means adapted to produce rectangular-wavepulses responsive to the output of said pulse amplifying means, clippingand summing means responsive to the output indications from saidsaturating amplifier means adapted to provide a direct voltage, theamplitude of which is functionally related to the frequency of thepulses from said radiation detecting means, and means responsive to theattainment of a predetermined amplitude by the output voltage of saidclipping and summing means during a given portion of a given operatingcycle of said loom adapted to continue operation of said loom for anadditional cycle of operation and to stop said loom in the event thatsaid output voltage of said clipping and summing means fails to attainsaid given amplitude during said given portion of said given operatingcycle.

3. In protection means for a loom operating with a yarn carrier whichwhen running on time passes a given point along the path thereof at agiven time in the loom cycle, an electric motor for driving said loom,radioactive means implanted in said yarn carrier, radiation detectingmeans stationed at a position whereat radiation particles from saidradioactive means will be detected when said shuttle passes said givenpoint, pulse amplifying means responsive to the output indications fromsaid radiation detecting means, saturating amplifier means adapted toproduce rectangular-Wave pulses responsive to the output of said pulseamplifying means, clipping and summing means responsive to the outputindications from said saturating amplifier means adapted to provide adirect voltage, the amplitude of which is functionally related to thefrequency of the pulses from said radiation detecting means, and meansresponsive to the attainment of a predetermined amplitude by the outputvoltage of said clipping and summing means during a given portion of agiven operating cycle of said loom adapted to continue operation of saidloom for an additional cycle of operation and to brake said motor in theevent that said output voltage of said clipping and summing means failsto attain said given amplitude during said given portion of said givenoperating cycle.

4. In a loom having a driving motor and a yarn carrier actuated therebyin a normal timed sequence, an energizing circuit and a brake circuitfor said driving motor, switch means adapted to connect said energizingcircuit to drive said motor in a first position and to connect saidbrake circuit to said motor in a second normal position, first meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a firstpredetermined time interval in each cycle of said travel, second meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a secondpredetermined time interval in each cycle of said motor overlapping saidfirst time interval and extending over the major portion of said eachcycle not covered by said first time interval and responsive to anelectrical signal having a given characteristic, radioactive sourcemeans carried by said yarn carrier, radiation detection means disposedat a point in the path of said carrier corresponding to the beginning ofsaid second time interval, and means coupling said radiation detectionmeans to said second means adapted to generate said electrical signal ofsaid given characteristic responsive to output indications from saidradiation detection means.

5. In a loom having a driving motor and a yarn carrier actuated therebyin a normal timed sequence, an energizing circuit and a brake circuitfor said driving motor, switch means adapted to connect said energizingcircuit to drive said motor in a first position and to connect saidbrake circuit to said motor in a second normal position, first meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a firstpredetermined time interval in each cycle of said travel, second meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a secondpredetermined time interval in each cycle of said motor overlapping saidfirst time interval and extending over the major portion of said eachcycle not covered by said first time interval responsive to anelectrical signal having a given characteristic, radioactive sourcemeans carried by said yarn carrier, radiation detection means disposedat a point in the path of said carrier corresponding to the beginning ofsaid second time interval, said second means comprising a gas dischargetube having at least cathode, plate, and control electrodes, the platecircuit of said tube including the actuating coil of said switch means,means coupling said control grid of said tube to said radiationdetection means over said second time interval adapted to fire said tuberesponsive to output signals from said radiation detection meansproduced by the detection of emanations from said radioactive sound, andmeans connected to the plate of said tube adapted to extinguish saidtube at a predetermined time in said cycle of loom during said firstpredetermined time interval.

6. In a loom having a driving motor and a yarn carrier actuated therebyin a normal timed sequence, an energizing circuit and a brake circuitfor said driving motor, switch means adapted to connect said energizingcircuit to drive said motor in a first position and to connect saidbrake circuit to said motor in a second normal position, first meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a firstpredetermined time interval in each cycle of said travel, second meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a secondpredetermined time interval in each cycle of said motor overlapping saidfirst time interval and extending over the major portion of said eachcycle not covered by said first time interval responsive to anelectrical signal having a given characteristic, radioactive sourcemeans carried by said yarn carrier, radiation detection means disposedat a point in the path of said carrier corresponding to the beginning ofsaid second time interval, said second means comprising a gas dischargetube having at least cathode, plate, and control electrodes, the platecircuit of said tube including the actuating coil of said switch means,means coupling said control grid of said tube to said radiationdetection means over said second time interval adapted to fire said tuberesponsive to output signals from said radiation detection meansproduced by the detection of emanations from said radioactive source,and switch means coupled to said motor adapted to couple anextinguishing voltage between said cathode and plate electrodes at apredetermined time during said first predetermined time interval.

7. in a loom having a driving motor and a yarn carrier actuated therebyin a normal timed sequence, an energizing circuit and a brake circuitfor said driving motor, switch means adapted to connect said energizingcircuit to drive said motor in a first position and to connect saidbrake circuit to said motor in a second normal position, first meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a firstpredetermined time interval in each cycle of said travel, second meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a secondpredetermined time interval in each cycle of said motor overlapping saidfirst time interval and extending over the major portion of said eachcycle not covered by said first time interval responsive to anelectrical signal having a given characteristic, radioactive sourcemeans carried by said yarn carrier, radiation detection means disposedat a point in the path of said carrier corresponding to the beginning ofsaid second time interval, said second means comprising a gas dischargetube having at least cathode, plate, and control electrodes, the platecircuit of said tube including the actuating coil of said switch means,saturating amplifier means coupled to said radiation detection meansadapted to convert output pulses from said detection means torectangular wave pulses of uniform amplitude, clipping and summing meansresponsive to the output of said saturating amplifier means adapted toproduce a direct voltage, the amplitude of which is functionally relatedto the frequency of pulses fed thereto, and switch means coupling saiddirect voltage to said control grid of said gas discharge tube to permitfiring of said gas discharge tube when said direct voltage reaches apredetermined amplitude.

8. In a loom having a driving motor and a yarn carrier actuated therebyin a normal timed sequence, an energizing circuit and a brake circuitfor said driving motor, switch means adapted to connect said energizingcircuit to drive said motor in a first position and to connect saidbrake circuit to said motor in a second normal position, first meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a firstpredetermined time interval in each cycle of said travel, second meansdriven by said motor and synchronized with normal carrier travel toactuate said switch means into said first position over a secondpredetermined time interval in each cycle of said motor overlapping saidfirst time interval and extending over the major portion of said eachcycle not covered by said first time interval responsive to anelectrical signal having a given characteristic, a source of betaradiation carried by said yarn carrier, radiation detection meansdisposed at a point in the path of said carrier corresponding to thebeginning of said second time interval, said second means comprising agas discharge tube having at least cathode, plate, and controlelectrodes, the plate circuit of said tube including the actuating coilof said switch means, saturating amplifier means coupled to saidradiation detection means adapted to convert output pulses from saiddetection means to rectangular wave pulses of uniform amplitude,clipping and summing means responsive to the output of said saturatingamplifier means adapted to produce a direct voltage, the amplitude ofwhich is functionally related to the frequency of pulses fed thereto,and switch means coupling said direct voltage to said control grid ofsaid gas discharge tube to permit firing of said gas discharge tube whensaid direct voltage reaches a predetermined amplitude.

9. In a motor control system, in combination: a cyclically-operatingwork mechanism, an electric motor driving said work mechanism throughits cycle, first means adapted to control operation of said electricmotor in accordance with electrical indications received thereby duringpredetermined portions of said cycle, second means for initiating saidindications including a radioactive source means, radiation detectingmeans responsive to emanations from said radioactive source, one of saidradioactive source means and said radiation detection means beingcarried by said work mechanism and the other being stationed relativethereto so that said detection means receives said emanations onlyduring said predetermined portions of said cycle, said first means beingcoupled to said second means and responsive to indications therefrom.

References Cited in the file of this patent UNITED STATES PATENTS2,456,233 Wolf Dec. 14, 1948 2,501,560 Blau Mar. 21, 1950 2,567,751Wolke Sept. 11, 1951 2,586,335 Howe et a1. Feb. 19, 1952 2,586,371 Mosset al Feb. 19, 1952 2,670,014 Hutchinson Feb. 23, 1954 2,692,951 VoelkerOct. 26, 1954

